<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>06_计算器练习</title>
</head>
<body>
<input type="text" id="i1"> <br>
<input type="text" id="i2"> <br>
<button onclick="calc('+')">加</button>
<button onclick="calc('-')">减</button>
<button onclick="calc('*')">乘</button>
<button onclick="calc('/')">除</button>
<h4> 结果： <span></span></h4>



<script>
    let n1 = document.getElementById('i1').value;
    let n2 = document.getElementById('i2').value;


    function calc(o) {

        n1 = parseFloat(n1);
        n2 = parseFloat(n2);

        let spanE = document.querySelector('span');
        switch (o) {
            case '+':
                spanE.innerHTML = n1 + n2;
                break;
            case '-':
                spanE.innerHTML = n1 - n2;
                break;
            case '*':
                spanE.innerHTML = n1 * n2;
                break;
            case '/':

                if (n2 != 0) {
                    spanE.innerHTML = n1 / n2;
                } else {

                    alert("除数不能为0");
                }
                break;
        }


    }
</script>
</body>
</html>